I've been seeing a lot of surface action from bass in a stretch of river that I've been fishing- swirls, splashes, rolling and rising with their heads poking out of the water, backs out of the water, sometimes jumping clear of the water. Not just little ones, either. Good-sized fish.

I'm not seeing any emerging insects that might directly account for this. The insect action is mostly midges and a few small water striders. There are damselflies around, but only a few. There are mayflies around, but only a few. I saw maybe four or five Epeorus (white flies) popping up, in the early morning. No crane flies, no caddis.

What I do notice close to the surface is large schools of minnows, mostly about 1"- 1.5" long, hovering about a foot or two below the surface and feeding on something tiny, probably plankton.

I'm thinking that the plentiful minnows holding in the top water column are the likely source of all of the commotion. That's my best guess.

Am I wrong? Or are the bass chasing something else, up from the depths?

Whatever the case, what I've been trying up top hasn't been working- rubber legged hardbodied poppers and sliders, deer hair poppers, Shenk's Sculpins fished both dry and waterlogged, damselfly nymphs tied with flash that also resemble minnows, pearl zonkers...nada.

How do I crack the code, here? I'm not used to bass acting so selectively when they're feeding. Do I need to "match the hatch" with a small streamer, like a 1" marabou? Other than that, I'm out of ideas right now.

Barbless, I think you're probably on the right track. In my experience, larger river SMBs usually don't feed much on small insects high in the water column (there are exceptions to this). They prefer crayfish or other larger bottom macros. Or they want baitfish which they will smack high in the water column or in shallow riffles. The one piece of your puzzle that's missing is actual baitfish scattering across the surface. Usually when bass are hitting baitfish the minnows will flee by leaping out of the water and literally bouncing across the surface. Nevertheless, even if you haven't seen this, I'd bet they're eating minnows and would try a close imitation fished just under the surface.

What waters are you fishing? On the Delaware, the SMB can become very picky, especially this time of year. Low water, high temps, and an overabundance of food (shad) makes for tough fishing this time of year.

It is a help to hear that I may not be totally clueless about this, and that others have also had a tough time in similar situations.

I've been fishing the upper Potomac. And from the replies, I'm getting the idea that the bass are going after these schooling minnows.

I haven't noticed any minnows leaping clear of the water with bass chasing them. I've seen that before, but it was a different circumstance- minnows being chased by bass through the shallows.

The structure I've been fishing has mostly been fairly deep pools, 4' to 10', with a moderate current and clear water. The minnows are holding in fairly tight schools in the top 18" of the water column, all facing the current. Based on what I've seen and the comments, my guess is that the bass are accelerating after their prey vertically rather than horizontally- holding deep in the pools and then plowing upward with their mouths open wide. The minnows aren't so much being chased as ambushed, from below and behind. And they're so plentiful that the bass are probably after gathering several in one gulp when making their move.

As a result, I'm supposing that my problem has to do with the fact that the bass are keyed on these small minnows. Since they already have their meal ticket and their menu choice, they're aren't overly inclined to be distracted by some splashy frog or wounded minnow imitation- much less some circus-clown attractor fly.

As it happens, I do have some small marabou streamers that would work fairly closely as an imitation. So I'll try that out (didn't have them in my box today). But I wouldn't be surprised if I face the same problem as someone trying to fish during a blizzard hatch- too many naturals for the fish to take any special notice of an imitation. Because those minnows are as plentiful as a commercial aquarium tank full of guppies. A home aquarium dip net would bring up several at once.

Anyway, if that doesn't work, I guess I'll go back to drifting something deep, like a crayfish or a wooly bugger. Or, hmm, I'll try the little minnow imitations with a sink-tip line.

Even if nothing happens, it's really something to marvel at the richness of that habitat.

I have used a Shenk's White Minnow to catch SMB in the topwater column. This is a proven pattern over many years. These flies can be tied on any size hook and trimmed to any shape to match a specific baitfish. I have also thrown a little rainbow Krystal flash in with the white marabou tail for a little extra appeal. It may be worth a shot in your situation.

you need to tie a minnow pattern that matches the real ones exact. bass can get real picky just like trout on a hatch.....on the delaware now the shad are coming down the river and bass/striper get keyed in on them and won't hit anything else thrown at them..

Clouser floating minnow is a great fly also. I've been using it pretty much exclusively all summer & doing quite well. I've caught over 40-50 smallies on the same exact fly this summer. It's pretty beat-up at this point, but still catching fish. Check it out!

He said they were busting minnows, it's a perfect scenio---minnows grouped together either feeding or fighting current with bass down under them shooting up and grabbing them. best way I have come up with when they are like this is to tie a really close imitation and just hold the fly in the current near the minnows or just below. Usaully the bass will hit it thinking its hurt or disabled..Same method can be used on the delaware for the Y.O.Y. shad now..A good fly would be the schoolie fly I posted. bass will try and take them by the mouthful...